Investigators could not, however, discover what caused the fire in the open-top trash bin at Bremer Manufacturing Co., a Town of New Holstein foundry that makes aluminum sand castings. Investigators said they found nothing that indicates it was set intentionally.

The investigation was a joint effort by the Calumet County Sheriff’s Department, state Fire Marshal’s Office and federal Bureau of Alcohol, Tobacco, Firearms and Explosives.

The 69-page report recounts the observations of St. Anna Fire Chief Robert Thome, who was one of the first volunteer firefighters to arrive on the scene after a sheriff’s deputy reported the fire. Bremer was closed at the time.

Thome told investigators he saw an 18-inch “cherry red” hotspot at the base of the trash bin. Using a ladder to look inside the bin, he noticed one barrel that appeared to be very hot and saw sparks coming from aluminum shavings and other materials that were burning.

Firefighters sprayed water on the contents, which produced a lot of steam and bluish-green flames. Thome instructed them to add foam to the hose stream, but that intensified the production of sparks.

“Chief Thome began to signal for the foam to be stopped, and as he was turning away from the Dumpster, the explosion occurred,” the report says.

Seventeen firefighters were within 50 feet of the trash bin when the thunderous blast occurred. Koeser, 33, of Kiel, was operating a pump near the trash bin. His body was found 60 feet away.

The explosion peeled back the south wall of the container. Eight 55-gallon barrels were found around the damaged container, and two barrels were found inside.

Investigators discovered several holes in the south side of the bin where the steel had melted through.

An employee of Bremer told investigators he had used a skid loader to place a barrel of aluminum oxide dross, called slag, into the trash bin about six hours before the fire was reported. He said the barrel “would have been too hot to touch and that touching the barrel would produce a severe burn to the hand.”

More than half of the investigative report contains safety data sheets for materials used at Bremer Manufacturing.

One sheet says ALpHASET 9010 “may become unstable at high temperatures.”

Safety instructions for aluminum casting alloy 356, 319 and 535 caution against using water or moist sand to fight a fire if they are present. The instructions say a fire or explosion “may occur when material is in the form of dust and exposed to heat or flames, chemical reaction, or contact with powerful oxidizers.”

The instructions conclude, “Never put water on molten metal — it will explode.”
Another sheet recommends that for fires involving aluminum fines or chips, firefighters should use dry sand or Class D (combustible metals) extinguishing agents. “Do not use water or other liquids, foams or halogenated extinguishing agents,” it says.

Calls to Thome and Tom Dolack, president of Bremer Manufacturing, were not returned Tuesday.

Bremer is located about one mile west of St. Anna, an unincorporated community straddling the Calumet and Sheboygan county lines.